The medicinal and psychoactive properties of the Cannabis plant have been known for centuries. At present, Cannabis is not legally available in many States. However, there is growing pressure on politicians to legalize its use, especially for medicinal purposes.
Evidence suggests that Cannabis is a safe, versatile and potentially inexpensive drug. It has been reported as being beneficial to patients suffering from a wide range of symptoms experienced in connection with various, often very serious, medical conditions. For example, Cannabis has been used to alleviate symptoms associated with cancer, anorexia, AIDS, chronic pain, spacicity, glaucoma, arthritis, migraine and many other illnesses.
Cannabis is recognized as having anti-emetic properties and has been successfully used to treat nausea and vomiting in cancer patients undergoing chemotherapy.
Studies also report use of Cannabis in treating the weight loss syndrome of AIDS and in reducing intraocular pressure for the treatment of glaucoma. Cannabis is also reported to have muscle relaxing effects and anti-convulsant effects.
However, it is also well documented that these medicinal effects of Cannabis come at the cost of less desirable effects. It is alleged that the administration of Cannabis causes changes in mood, perception and motivation. The common euphoric effects have led to the use of Cannabis as a recreational, “soft” drug and its criminalization. The psychoactive effects are said to vary with dose, with the typical Cannabis smoker experiencing a “high” which lasts about 2 hours, during which there is impairment of cognitive functions, perception, reaction time, learning and memory. These side effects clearly have implications, such as for the operation of machinery, and in particular for driving. These effects also make Cannabis less attractive for widespread, mainstream use, as it can reduce a patient's ability to perform relatively simple tasks during treatment.
The euphoric effects of Cannabis may also constitute an undesirable side effect for patients using the drug for medicinal purposes, especially for “naive” Cannabis users. Furthermore, here have been reports of unpleasant reactions to Cannabis, such as anxiety, panic or hallucinations. It is believed that these undesirable effects are most commonly associated with higher doses of Cannabis. 
Despite these effects, years of research have failed to show that Cannabis is dangerous. In fact, the results appear to have proved the opposite. Cannabis has been shown to be safer, with fewer serious side effects than most prescription drugs currently used as anti-emetics, muscle relaxants, hypnotics and analgesics, etc.
The physiological and pharmacological effects of Cannabis depend upon a number of factors, including the dosage level and the route of administration.
There are currently two main methods of Cannabis delivery. Lung delivery is most commonly achieved by smoking Cannabis. Unfortunately, there are concerns about the effect of this mode of administration on the lungs. Cannabis smoke carries even more tars and other particulate matter than tobacco, and so may be a cause of lung cancer. Furthermore, many patients find the act of smoking unappealing, as well as generally unhealthy. It is known that some of the chemicals produced by smoking Cannabis are aggressive and smoking has been shown to cause the gradual dissolving of teeth. Use of vaporizers for inhalation administration of Cannabis does not avoid the production of thermal byproducts, and also can produce tracheal and lung irritation. For these reasons, smoking is not an approved medical means of administration for any drug.
Attempts have been made to overcome some of the problems associated with smoking both Cannabis and tobacco by providing various smokeless inhalable aerosol formulations for lung delivery. A self-propelled inhalable aerosol of delta-9-tetrahydrocannabinol was developed as long ago as 1975 as a bronchodilator. Inhalable aerosol formulations were made comprising either only liquid components and or including a solid particulate component carrying the active agent, such as the Cannabis. The various formulations were found to be of varying effectiveness in delivering the active agent to the alveoli of the lungs in the same manner as smoke.
However, both methods of lung delivery discussed above have been found to cause a pronounced and involuntary cough, possibly from irritation of the trachea and lungs. This unpleasant side effect is not overcome by the smoke-free method of lung delivery.
An oral dosage form of Cannabis is available in the United States as a Schedule II drug. The capsules contain a synthetic version of delta-9-tetrahydrocannabinol (delta-9-THC), the main active substance in Cannabis, and they have had limited success for a number of reasons. Firstly, in light of its anti-emetic properties, the capsules are commonly used to treat nausea and vomiting. Clearly, an oral administration is not ideal as the patient may well have difficulty keeping the capsule down long enough for it to take effect. It has also been found that orally administered THC is erratically and slowly absorbed into the bloodstream, making the dose and duration of action difficult to control. Furthermore, the oral dose is less effective than smoked Cannabis and therefore larger doses are required in order to achieve a desired therapeutic effect.